The Prediction of Radiation-Induced Trismus by the Apparent Diffusion Coefficient Values of Masseter Muscles before Chemoradiotherapy in Locally Advanced Nasopharyngeal Carcinomas

Abstract

Purpose: Although the apparent diffusion coefficient (ADC) value from diffusion-weighted imaging can provide insights into various pathological processes, no studies have examined the relationship between the pre-concurrent chemoradiotherapy (CCRT) mean ADC (ADCmean) values of the masseter muscles and radiation-induced trismus (RIT) in locally advanced nasopharyngeal carcinoma (LA-NPC) patients. Therefore, the current research aimed to investigate the significance of pre-CCRT masseter muscle ADCmean values for predicting the RIT rates in LA-NPC patients treated with definitive CCRT. Materials and Methods: The pre-CCRT ADCmean values of the masseter muscles and the post-CCRT RIT rates were evaluated. A receiver operating characteristic curve analysis was employed to determine the optimal ADCmean cutoff. The primary objective was to examine the relationship between the pre-CCRT masseter muscle ADCmean values and the post-CCRT RIT rates. Results: Seventy-seven patients were included. The optimal ADCmean cutoff value was 1381.30 × 10−6 mm2/s, which divided the patients into two groups: an ADCmean −6 mm2/s (n = 49) versus an ADCmean > 1381.30 × 10−6 mm2/s (n = 28). A masseter muscle ADCmean > 1381.30 × 10−6 mm2/s was found to be associated with significantly higher RIT rates than an ADCmean −6 mm2/s (71.42% vs. 6.12%; p mean > 1381.30 × 10−6 mm2/s as an independent predictor of RIT. Conclusions: Our study presents the first evidence establishing a connection between elevated masseter muscle ADCmean values and higher RIT rates in LA-NPC patients following CCRT. If confirmed with further research, these findings may help to categorize the risk of RIT in these patients.

Keywords

• apparent diffusion coefficient
• masseter muscle
• nasopharyngeal carcinoma
• radiation-induced trismus